1. A person who enjoys exploring the details of programmable systems
and how to stretch their capabilities, as opposed to most users, who prefer
to learn only the minimum necessary. RFC1392, the Internet
Users' Glossary, usefully amplifies this as: A person who
delights in having an intimate understanding of the internal workings of a
system, computers and computer networks in particular.

2. One who programs enthusiastically (even obsessively) or who
enjoys programming rather than just theorizing about programming.

5. An expert at a particular program, or one who frequently does
work using it or on it; as in ‘a Unix hacker’. (Definitions 1
through 5 are correlated, and people who fit them congregate.)

6. An expert or enthusiast of any kind. One might be an astronomy
hacker, for example.

7. One who enjoys the intellectual challenge of creatively
overcoming or circumventing limitations.

8. [deprecated] A malicious meddler who tries to discover sensitive
information by poking around. Hence password
hacker, network hacker.
The correct term for this sense is cracker.

The term ‘hacker’ also tends to connote membership in the
global community defined by the net (see
the network. For discussion of some of the basics of this culture,
see the How
To Become A Hacker FAQ. It also implies that the person described
is seen to subscribe to some version of the hacker ethic (see
hacker ethic).

It is better to be described as a hacker by others than to describe
oneself that way. Hackers consider themselves something of an elite (a
meritocracy based on ability), though one to which new members are gladly
welcome. There is thus a certain ego satisfaction to be had in identifying
yourself as a hacker (but if you claim to be one and are not, you'll
quickly be labeled bogus). See also
geek, wannabee.

This term seems to have been first adopted as a badge in the 1960s by
the hacker culture surrounding TMRC and the MIT AI Lab. We have a report
that it was used in a sense close to this entry's by teenage radio hams and
electronics tinkerers in the mid-1950s.